1. Technical Field
This U.S. Utility application claims priority to India Application No. 2498/MUM/2015, filed Jun. 30, 2015, and is incorporated herein by reference.
The subject matter described herein in general relates to a catalyst composition for isomerization of paraffins comprising of at least one metal, at least one heteropoly acid and a support material. The invention also relates to a process for the preparation of a catalyst composition for isomerization of paraffins. The invention further relates to a process for isomerization of paraffins using the catalytic composition.
2. Related Art
Isomerization of paraffins is important for the conversion of n-pentane and n-hexane into their respective isoparaffins of substantially higher octane number, and to provide additional feedstock for alkylation units. Several catalytic methods are known for paraffins isomerization. Skeletal isomerization of n-pentane in the presence of hydrogen has been studied over Pt-promoted H3PW12O40 (TPA)/MCM-41 bifunctional catalyst. A series of solid acid catalysts with different loading amount of TPA and Pt were prepared and characterized by XRD, FT-IR and XPS. The optimal catalytic activity of Pt-TPA/MCM-41 was observed with 2% Pt and 30% TPA. According to the cracked products distribution, this is typical of a monomolecular bifunctional metal-acid mechanism. Further, catalysts with different combination of noble metals (Pt, Pd and Ru), heteropoly acids (HPAs) (TPA, tungstosilicic acid (TSA), and molybdophosphoric acid (MPA)) and supports (MCM-41, SBA-1 and SiO2) were also synthesized and their catalytic performances were compared. (Xu, Yuandong, et al., Catalysis Letters, 125.1-2, 2008, 83-89.) In another report n-pentane isomerization over Pt- and Ni—Pt-promoted sulfated zirconia catalysts supported on alumina was studied in which two series of sulfated zirconia catalysts promoted with Pt and Pt—Ni, respectively, were prepared and extruded with different amount of alumina binder (0, 20, 33, and 60 wt %). The catalytic activities of the two series of catalysts, SZPtA and SZNiPtA, were measured for n-pentane isomerization reaction. The reaction reaches its maximum conversion at 20 wt % of alumina for both catalyst series. Adding alumina beyond 20 wt % reduces the overall conversion and modifies the selectivity for both catalysts series from i-C4 towards i-C5 suggesting that the reaction mechanism changed from a monomolecular to a bimolecular one. However, only SZNiPtA catalysts maintain a higher catalytic activity at higher amounts of alumina. Such difference between the two catalyst series can be attributed to the combining effect of Ni and Pt promotion of the SZNiPtA catalysts and not to their acidic properties. But it was seen that Zirconia deactivated at a faster rate however using Pt noble metal was expensive and the conversion was predominantly affected by the alumina content (Pérez-Luna, M., et al., Catalysis letters 131.1-2, 2009, 285-293.)
US20040222132 discloses a process for the upgrading of hydrocarbon mixtures which boil within the naphtha range containing sulfur impurities, i.e., a hydrodesulfuration process with contemporaneous skeleton isomerization and reduced hydrogenation degree of the olefins contained in said hydrocarbon mixtures, the whole process being carried out in a single step. The process is carried out in the presence of a catalytic system comprising a metal of group VI B, a metal of group VIII and a carrier of acid nature consisting of a mesoporoussilico-alumina.
U.S. Pat. No. 5,576,256 describes a hydroconversion catalyst composition including a catalytically active matrix having a surface area of between about 50 m2/g to about 290 m2/g, a silicious molecular sieve support medium distributed through the matrix and having a surface area of between about 250 m2/g to about 1200 m2/g and a catalytically active phase supported on the support medium and including a first metal selected from group IIIA of the periodic table of elements and a second metal selected from group VIB of the periodic table of elements. The matrix preferably further includes aluminum, gallium, cobalt, molybdenum, and phosphorus.
U.S. Pat. No. 5,256,277 describes paraffins, especially paraffins in the C4-C8 range, which are isomerized to iso-paraffins over an isomerization catalyst comprising a noble metal such as platinum on a support material comprising an inorganic, non-layered, porous, crystalline phase aluminosilicate material with pores of at least 13 Å and which exhibits, after calcination, an X-ray diffraction pattern with at least one peak at a d-spacing greater than 18 Å. These materials have a high surface area and sorption capacity marked by a benzene adsorption capacity of greater than about 15 grams benzene per 100 grams at 50 torr and 25° C. In its preferred form, the support material has a uniform, hexagonal arrangement of pores with diameters of at least about 13 Å and a hexagonal electron diffraction pattern that can be indexed with a d100 value greater than about 18 Å which corresponds to at least one peak in the X-ray diffraction pattern.